As a method for bonding a corrosion resistant metal lining (such as Ti (titanium) or Zr (zirconium)) to an Fe (iron)-based or a Cu (copper)-based metal substrate, various methods, such as explosion bonding, rolling process and spot welding, has been proposed or performed. In the explosion bonding process, a corrosion resistant metal plate and a metal substrate are overlapped and bonded by a charge of explosive powder placed thereon. In the rolling process, a corrosion resistant metal plate and a metal substrate are overlapped and roll-bonded together between a pair of rolls.
However, following problem may occur in the conventional method described above.
(1) In explosion bonding, the sites for performing the process may be limited because of the noise accompanying the explosion detonation. In addition, the production costs are relatively high, and the shape and/or dimension of the cladding material is limited. Furthermore, numerous production steps are necessary for producing a thin plate-like cladding material, because only a thick material is directly produced by means of explosive bonding, and consequently a rolling operation is necessary to obtain a thin one.
(2) The rolling process typically requires an expensive rolling facility and cannot cover irregular shapes or curvature of the substrate. Therefore the only possible shape is only a flat plate. The bonding force between the substrate and the lining typically tends to be weaker than that achieved by the explosion bonding process, so that in many cases an additional diffusion heat treatment is needed for securing the bonding strength. This may lead to an increase in the steps and cost of the process.
(3) The spot welding process is time-consuming since many spot-welded portion should be formed to bond the substrate and the lining. Furthermore, each welded portion is formed in a spot-like shape, so that the bonding force at the welded portion is relatively weak, and a strong sealing is not achieved between the substrate and the lining.
The object of this invention is to offer a cladding material which is produced easily by using seam welding process and has an excellent bonding strength.